Costa Rica is a beautiful country with very friendly people and you will feel safe driving through small rural towns. However, like everywhere in the world, there is crime and you need to use your best judgment. You should make copies of all important travel docs including your passport and put them in a separate place than the originals. Never leave your valuables in your car unattended. A good rule of thumb is to get to where you are going, drop off your stuff in your hotel or house and then go to the beach, restaurant etc. Also, if you are a young traveler be aware of locals that speak good English and want to be your friend and tour guide. Some of them may take your stuff while you’re not looking.